how to stop re-rendering of child component if parent update the context or state in react js ?
I am already using React.memo still it is re-rendering.
this is my child component
const Ab = () => {
console.log("---ff-ddd");
const pageContext = useContext(PageContext);
useEffect(() => {
setTimeout(() => {
pageContext.updateGlobalMenu({});
}, 5000);
}, []);
return <div>ddd</div>;
};
export default React.memo(Ab);
I am updating the context. I want it update the context value but not re-render the child component
export default function IndexPage() {
const [globalMenu, setGlobalMenu] = useState("");
const updateGlobalMenu = (menuContent) => {
setGlobalMenu(menuContent);
};
return (
<PageContext.Provider
value={{
updateGlobalMenu
}}
>
<Ab />
</PageContext.Provider>
);
}
here is my code
https://codesandbox.io/s/friendly-bartik-3cnqvf?file=/pages/index.js:156-470
if you see it print two times console. it means it is re-rendering two times
If PageContext's value changes, then any component consuming that context (including Ab) will render. React.memo cannot stop this. In your case you're changing the value on every render, so you have room to improve it by memoizing the context value. That way, the value won't change unless it needs to:
export default function IndexPage() {
const [globalMenu, setGlobalMenu] = useState("");
const updateGlobalMenu = useCallback((menuContent) => {
setGlobalMenu(menuContent);
}, []);
const value = useMemo(() => ({
updateGlobalMenu
}), [updateGlobalMenu]);
return (
<PageContext.Provider value={value}>
<Ab />
</PageContext.Provider>
);
}
You can also, in addition to memoisation from the previous answer, split your "api" and "data" portion of the state into two different providers.
updateGlobalMenu will be in PageContextAPI provider, globalMenu will be in PageContextData provider. That way when you update the data, only the provider with the data will be re-rendered.
Take a look at this article, I covered this technique in detail here:https://www.developerway.com/posts/how-to-write-performant-react-apps-with-context
I would like to figure out how to subscribe on updates of a stored value it the redux store.
So far I've tried something like the following:
<ReactReduxContext.Consumer>
{({store}) => {
console.log('store:', store.getState());
const p = <p>{store.getState().value}</p>;
store.subscribe(() => {p.innerText = store.getState().value});
return p;
}}
</ReactReduxContext.Consumer>
bumping into the TypeError: can't define property "innerText": Object is not extensible error on updates.
So I wonder how to update the contents?
There are a few things about your code that are just not the way that we do things in React.
React is its own system for interacting with the DOM, so you should not attempt direct DOM manipulation through .innerText. Your code doesn't work because the variable p which you create is a React JSX Element rather than a raw HTML paragraph element, so it doesn't have properties like innerText.
Instead, you just return the correct JSX code based on props and state. The code will get updated any time that props or state change.
The ReactReduxContext is used internally by the react-redux package. Unless you have a good reason to use it in your app, I would not recommend it. There are two built-in ways that you can get a current value of state that is already subscribed to changes.
useSelector hook
(recommended)
export const MyComponent1 = () => {
const value = useSelector(state => state.value);
return <p>{value}</p>
}
connect higher-order component
(needed for class components which cannot use hooks)
class ClassComponent extends React.Component {
render() {
return <p>{this.props.value}</p>
}
}
const mapStateToProps = state => ({
value: state.value
});
const MyComponent2 = connect(mapStateToProps)(ClassComponent)
ReactReduxContext
(not recommended)
If anyone reading this has a good reason why they should need to use store.subscribe(), proper usage would look something like this:
const MyComponent3 = () => {
const { store } = useContext(ReactReduxContext);
const [state, setState] = useState(store.getState());
useEffect(() => {
let isMounted = true;
store.subscribe(() => {
if (isMounted) {
setState(store.getState());
}
});
// cleanup function to prevent calls to setState on an unmounted component
return () => {
isMounted = false;
};
}, [store]);
return <p>{state.value}</p>;
};
CodeSandbox Demo
I am using Redux with Class Components in React. Having the below two states in Redux store.
{ spinner: false, refresh: false }
In Parent Components, I have a dispatch function to change this states.
class App extends React.Component {
reloadHandler = () => {
console.log("[App] reloadComponent");
this.props.onShowSpinner();
this.props.onRefresh();
};
render() {
return <Child reloadApp={this.reloadHandler} />;
}
}
In Child Component, I am trying to reload the parent component like below.
class Child extends React.Component {
static getDerivedStateFromProps(props, state) {
if (somecondition) {
// doing some redux store update
props.reloadApp();
}
}
render() {
return <button />;
}
}
I am getting error as below.
Warning: Cannot update a component from inside the function body of a
different component.
How to remove this warning? What I am doing wrong here?
For me I was dispatching to my redux store in a React Hook. I had to dispatch in a useEffect to properly sync with the React render cycle:
export const useOrderbookSubscription = marketId => {
const { data, error, loading } = useSubscription(ORDERBOOK_SUBSCRIPTION, {
variables: {
marketId,
},
})
const formattedData = useMemo(() => {
// DISPATCHING HERE CAUSED THE WARNING
}, [data])
// DISPATCHING HERE CAUSED THE WARNING TOO
// Note: Dispatching to the store has to be done in a useEffect so that React
// can sync the update with the render cycle otherwise it causes the message:
// `Warning: Cannot update a component from inside the function body of a different component.`
useEffect(() => {
orderbookStore.dispatch(setOrderbookData(formattedData))
}, [formattedData])
return { data: formattedData, error, loading }
}
If your code calls a function in a parent component upon a condition being met like this:
const ListOfUsersComponent = ({ handleNoUsersLoaded }) => {
const { data, loading, error } = useQuery(QUERY);
if (data && data.users.length === 0) {
return handleNoUsersLoaded();
}
return (
<div>
<p>Users are loaded.</p>
</div>
);
};
Try wrapping the condition in a useEffect:
const ListOfUsersComponent = ({ handleNoUsersLoaded }) => {
const { data, loading, error } = useQuery(QUERY);
useEffect(() => {
if (data && data.users.length === 0) {
return handleNoUsersLoaded();
}
}, [data, handleNoUsersLoaded]);
return (
<div>
<p>Users are loaded.</p>
</div>
);
};
It seems that you have latest build of React#16.13.x. You can find more details about it here. It is specified that you should not setState of another component from other component.
from the docs:
It is supported to call setState during render, but only for the same component. If you call setState during a render on a different component, you will now see a warning:
Warning: Cannot update a component from inside the function body of a different component.
This warning will help you find application bugs caused by unintentional state changes. In the rare case that you intentionally want to change the state of another component as a result of rendering, you can wrap the setState call into useEffect.
Coming to the actual question.
I think there is no need of getDerivedStateFromProps in the child component body. If you want to trigger the bound event. Then you can call it via the onClick of the Child component as i can see it is a <button/>.
class Child extends React.Component {
constructor(props){
super(props);
this.updateState = this.updateState.bind(this);
}
updateState() { // call this onClick to trigger the update
if (somecondition) {
// doing some redux store update
this.props.reloadApp();
}
}
render() {
return <button onClick={this.updateState} />;
}
}
Same error but different scenario
tl;dr wrapping state update in setTimeout fixes it.
This scenarios was causing the issue which IMO is a valid use case.
const [someState, setSomeState] = useState(someValue);
const doUpdate = useRef((someNewValue) => {
setSomeState(someNewValue);
}).current;
return (
<SomeComponent onSomeUpdate={doUpdate} />
);
fix
const [someState, setSomeState] = useState(someValue);
const doUpdate = useRef((someNewValue) => {
setTimeout(() => {
setSomeState(someNewValue);
}, 0);
}).current;
return (
<SomeComponent onSomeUpdate={doUpdate} />
);
In my case I had missed the arrow function ()=>{}
Instead of onDismiss={()=>{/*do something*/}}
I had it as onDismiss={/*do something*/}
I had same issue after upgrading react and react native, i just solved that issue by putting my props.navigation.setOptions to in useEffect. If someone is facing same problen that i had i just want to suggest him put your state changing or whatever inside useEffect
Commented some lines of code, but this issue is solvable :) This warnings occur because you are synchronously calling reloadApp inside other class, defer the call to componentDidMount().
import React from "react";
export default class App extends React.Component {
reloadHandler = () => {
console.log("[App] reloadComponent");
// this.props.onShowSpinner();
// this.props.onRefresh();
};
render() {
return <Child reloadApp={this.reloadHandler} />;
}
}
class Child extends React.Component {
static getDerivedStateFromProps(props, state) {
// if (somecondition) {
// doing some redux store update
props.reloadApp();
// }
}
componentDidMount(props) {
if (props) {
props.reloadApp();
}
}
render() {
return <h1>This is a child.</h1>;
}
}
I got this error using redux to hold swiperIndex with react-native-swiper
Fixed it by putting changeSwiperIndex into a timeout
I got the following for a react native project while calling navigation between screens.
Warning: Cannot update a component from inside the function body of a different component.
I thought it was because I was using TouchableOpacity. This is not an issue of using Pressable, Button, or TouchableOpacity. When I got the error message my code for calling the ChatRoom screen from the home screen was the following:
const HomeScreen = ({navigation}) => {
return (<View> <Button title = {'Chats'} onPress = { navigation.navigate('ChatRoom')} <View>) }
The resulting behavior was that the code gave out that warning and I couldn't go back to the previous HomeScreen and reuse the button to navigate to the ChatRoom. The solution to that was doing the onPress in an inline anonymous function.
onPress{ () => navigation.navigate('ChatRoom')}
instead of the previous
onPress{ navigation.navigate('ChatRoom')}
so now as expected behavior, I can go from Home to ChatRoom and back again with a reusable button.
PS: 1st answer ever in StackOverflow. Still learning community etiquette. Let me know what I can improve in answering better. Thanx
If you want to invoke some function passed as props automatically from child component then best place is componentDidMount lifecycle methods in case of class components or useEffect hooks in case of functional components as at this point component is fully created and also mounted.
I was running into this problem writing a filter component with a few text boxes that allows the user to limit the items in a list within another component. I was tracking my filtered items in Redux state. This solution is essentially that of #Rajnikant; with some sample code.
I received the warning because of following. Note the props.setFilteredItems in the render function.
import {setFilteredItems} from './myActions';
const myFilters = props => {
const [nameFilter, setNameFilter] = useState('');
const [cityFilter, setCityFilter] = useState('');
const filterName = record => record.name.startsWith(nameFilter);
const filterCity = record => record.city.startsWith(cityFilter);
const selectedRecords = props.records.filter(rec => filterName(rec) && filterCity(rec));
props.setFilteredItems(selectedRecords); // <-- Danger! Updates Redux during a render!
return <div>
<input type="text" value={nameFilter} onChange={e => setNameFilter(e.target.value)} />
<input type="text" value={cityFilter} onChange={e => setCityFilter(e.target.value)} />
</div>
};
const mapStateToProps = state => ({
records: state.stuff.items,
filteredItems: state.stuff.filteredItems
});
const mapDispatchToProps = { setFilteredItems };
export default connect(mapStateToProps, mapDispatchToProps)(myFilters);
When I ran this code with React 16.12.0, I received the warning listed in the topic of this thread in my browser console. Based on the stack trace, the offending line was my props.setFilteredItems invocation within the render function. So I simply enclosed the filter invocations and state change in a useEffect as below.
import {setFilteredItems} from './myActions';
const myFilters = props => {
const [nameFilter, setNameFilter] = useState('');
const [cityFilter, setCityFilter] = useState('');
useEffect(() => {
const filterName = record => record.name.startsWith(nameFilter);
const filterCity = record => record.city.startsWith(cityFilter);
const selectedRecords = props.records.filter(rec => filterName(rec) && filterCity(rec));
props.setFilteredItems(selectedRecords); // <-- OK now; effect runs outside of render.
}, [nameFilter, cityFilter]);
return <div>
<input type="text" value={nameFilter} onChange={e => setNameFilter(e.target.value)} />
<input type="text" value={cityFilter} onChange={e => setCityFilter(e.target.value)} />
</div>
};
const mapStateToProps = state => ({
records: state.stuff.items,
filteredItems: state.stuff.filteredItems
});
const mapDispatchToProps = { setFilteredItems };
export default connect(mapStateToProps, mapDispatchToProps)(myFilters);
When I first added the useEffect I blew the top off the stack since every invocation of useEffect caused state change. I had to add an array of skipping effects so that the effect only ran when the filter fields themselves changed.
I suggest looking at video below. As the warning in the OP's question suggests, there's a change detection issue with the parent (Parent) attempting to update one child's (Child 2) attribute prematurely as the result of another sibling child's (Child 1) callback to the parent. For me, Child 2 was prematurely/incorrectly calling the passed in Parent callback thus throwing the warning.
Note, this commuincation workflow is only an option. I personally prefer exchange and update of data between components via a shared Redux store. However, sometimes it's overkill. The video suggests a clean alternative where the children are 'dumb' and only converse via props mand callbacks.
Also note, If the callback is invoked on an Child 1 'event' like a button click it'll work since, by then, the children have been updated. No need for timeouts, useEffects, etc. UseState will suffice for this narrow scenario.
Here's the link (thanks Masoud):
https://www.youtube.com/watch?v=Qf68sssXPtM
In react native, if you change the state yourself in the code using a hot-reload I found out I get this error, but using a button to change the state made the error go away.
However wrapping my useEffect content in a :
setTimeout(() => {
//....
}, 0);
Worked even for hot-reloading but I don't want a stupid setTimeout for no reason so I removed it and found out changing it via code works just fine!
I was updating state in multiple child components simultaneously which was causing unexpected behavior. replacing useState with useRef hook worked for me.
Try to use setTimeout,when I call props.showNotification without setTimeout, this error appear, maybe everything run inTime in life circle, UI cannot update.
const showNotifyTimeout = setTimeout(() => {
this.props.showNotification();
clearTimeout(showNotifyTimeout);
}, 100);
I have this code.
and here is the code snippet
const [indicators, setIndicators] = useState([]);
const [curText, setCurText] = useState('');
const refIndicator = useRef()
useEffect(() => {
console.log(indicators)
}, [indicators]);
const onSubmit = (e) => {
e.preventDefault();
setIndicators([...indicators, curText]);
setCurText('')
}
const onChange = (e) => {
setCurText(e.target.value);
}
const MemoInput = memo((props)=>{
console.log(props)
return(
<ShowIndicator name={props.name}/>
)
},(prev, next) => console.log('prev',prev, next)
);
It shows every indicator every time I add in the form.
The problem is that ShowIndicator updates every time I add something.
Is there a way for me to limit the the time my App renders because for example I created 3 ShowIndicators, then it will also render 3 times which I think very costly in the long run.
I'm also thinking of using useRef just to not make my App renders every time I input new text, but I'm not sure if it's the right implementation because most documentations recommend using controlled components by using state as handler of current value.
Observing the given sandbox app behaviour, it seems like the whole app renders for n times when there are n indicators.
I forked the sandbox and moved the list to another functional component (and memo'ed it based on prev and next props.
This will ensure my 'List' is rendered every time a new indicator is added.
The whole app will render only when a new indicator is added to the list.
Checkout this sandbox forked from yours - https://codesandbox.io/embed/avoid-re-renders-react-l4rm2
React.memo will stop your child component rendering if the parent rerenders (and if the props are the same), but it isn't helping in your case because you have defined the component inside your App component. Each time App renders, you're creating a new reference of MemoInput.
Updated example: https://codesandbox.io/s/currying-tdd-mikck
Link to Sandbox:
https://codesandbox.io/s/musing-kapitsa-n8gtj
App.js
// const MemoInput = memo(
// props => {
// console.log(props);
// return <ShowIndicator name={props.name} />;
// },
// (prev, next) => console.log("prev", prev, next)
// );
const renderList = () => {
return indicators.map((data,index) => {
return <ShowIndicator key={index} name={data} />;
});
};
ShowIndicator.js
import React from "react";
const ShowIndicator = ({ name }) => {
console.log("rendering showIndicator");
const renderDatas = () => {
return <div key={name}>{name}</div>;
};
return <>{renderDatas()}</>;
};
export default React.memo(ShowIndicator); // EXPORT React.memo
This question already has answers here:
Reactjs - Setting State from props using setState in child component
(2 answers)
Closed 5 years ago.
So as I understand, a component will re-render when there has been a change in props and componentWillMount shall run before re-rendering. At the moment my constructor and componentWillMount run as expected, but then the question prop changes which I need to update the user score state, but this change in question prop doesn't trigger the constructor or componentWillMount. As I shouldn't update the state inside the render function (the only place so far that I have been able to get access to the updated question prop), how can I make react recognise this change in it's props and then update the state? Hope that's understandable.
Here is my container
class FullTimeScoreContainer extends Component<Props, State> {
constructor(props: Props) {
super(props)
this.state = {
userHomeScore: 1,
userAwayScore: 1
}
}
componentWillMount() {
getFTSAnswerStatus(this.props.question).then(foundScores => {
if ( foundScores.userHomeScore ) {
this.setState({
userHomeScore: foundScores.userHomeScore,
userAwayScore: foundScores.userAwayScore
});
}
})
}
render() {
const { option, question, questionIndex, user, configs, renderAs, showNextQuestionAfterFTS, total} = this.props;
// check if question is active or not
let ComponentClass;
if ( question[0].active ) {
ComponentClass = FullTimeScoreActive;
} else {
ComponentClass = FullTimeScoreLocked;
}
const changeScoreState = (team, val) => {
switch (team) {
case "home":
this.setState( (prevState) => ({ userHomeScore: prevState.userHomeScore + val }) );
break;
case "away":
this.setState( (prevState) => ({ userAwayScore: prevState.userAwayScore + val }) );
break;
default:
throw new Error("unrecognised team to change score state")
}
}
const onClickCallback = () => {
const p = this.props;
const s = this.state;
p.showNextQuestionAfterFTS();
p.recordFullTimeScoreAnswer(s.userHomeScore, s.userAwayScore, p.question, p.questionIndex, p.user, p.configs)
}
return (
<ComponentClass
imgSrc={imgSrc}
user={user}
answerStatus={answerStatus}
question={question}
onClickCallback={onClickCallback}
questionIndex={questionIndex}
total={total}
configs={configs}
userScores={this.state}
changeScoreState={changeScoreState}
/>
)
}
}
const mapStateToProps = state => {
return {
configs: state.configs,
user: state.user
};
}
function mapDispatchToProps(dispatch) {
return bindActionCreators({ recordFullTimeScoreAnswer, showNextQuestionAfterFTS }, dispatch);
};
export default connect(mapStateToProps, mapDispatchToProps)(FullTimeScoreContainer);
export { FullTimeScoreContainer }
componentWillMount will only run before the first render. It doesn't get run before every render. So even if your state and props update, componentWillMount will not get called again.
The constructor function is the same as well.
You might be looking for componentWillReceiveProps (see docs). This lifecycle event is called when a mounted component is about to receive new props. You can update your state in this lifecycle event.
Note that componentWillReceiveProps only works on mounted components. Therefore, it will not get called the first time your component receives its' initial props.
A side note: Per the docs, you also don't want to introduce any side-effects or subscriptions in componentWillMount. Do that in componentDidMount instead.
I would like add a comment, but I don't have enough reputation...
a component will re-render when there has been a change in props
As I understand, you can't change the props, so component re-render on state changes.